Uropods are often defined as the appendages of the last body segment of a crustacean.[1] An alternative definition suggested by Frederick R. Schram restricts the term to those structures arising from the segment before the anal segment (the segment which carries the anus).[1] Under this latter definition, the appendages of the anal segment are caudal rami, which are analogous to uropods.[1]

Uropods are typically biramous – comprising an endopod and an exopod. The exopod is typically the larger, and may be divided in two by a transverse suture known as the diaeresis.[2][3] The uropods may work in concert with the telson to form a "tail fan".[4]